We had a bloke round the other day to assess our house for cavity wall insulation. It's a 1930s detached.

He took one look and said he wouldn't touch it because he said it would likely cause damp. We have never had a problem with damp, but he said that cavity wall insulation would create damp because of the age of the house and the way they were built.

He then told us that we are probably losing 40% of our heat through the walls. He suggested the answer might be a new treatment coming out in the autumn where you attach panels to the outside of the house and render over.

Anyone else had cavity wall insulation conversations like this?

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If your outside wall is in sound order, there's no reason why cavity insulation should cause damp. However, if your house is rendered then you would need to be sure that there were no cracks through which damp could penetrate.

But I'm wondering if you actually have cavity walls Dave because if it was built in the 30s it will almost certainly be 9" solid brick. This might also be why he suggested applying a coating to the outside and rendering over. Many council houses of pre war build have been upgraded in this way, but it doesn't always improve the appearance as they use horrible looking fine stone render finish to save putting a hard outer surface on.

If you are 9" solid brick with render on the outside then your heat losses will be like ours were (with identical build), ie, horrendous. So do you want good appearance or low heating bills?

Do you have any bare brickwork in the roof space? If so, you could prove whether or not you have a solid wall by looking at the bonding. Or you could just measure the wall thickness by an original opening, adding on about 2" for the internal plaster and external render.

we had loft insulation and it caused huge problems in the loft with condensation as it was tucked to close to the eaves and blocked airflow. now sorted thankfully.

we have had cavity done in an 80s build house with no issues at all.

i guess you have to find out if its damp or condensation he's talking about.

with cavity wall installs they will put a vent in to your wall to prevent condensation. This is a compulsory building regs thing. My vent is now blocked up as it was too cold in the winter and all is fine after 2 years.

I wonder if the person making this suggestion has a vested interest in this new method and is trying to buy time so he can offer that when the time comes? I believed this was being introduced for houses without cavity walls. By the sound of it, this new method will be considerably more expensive and therefore potentially more lucrative for installers. I also remember the horror stories of its predecessor the 'dreaded stone cladding brigade' that so blighted victims in the 1970's. The new insulation method will involve changing the appearance of houses and some are expressing concern about the affect that will have on the overall appearance of towns and villages. Of course many properties have already had successful external cladding, this can be seen in some Council houses in Welham Green which have solid walls and were clad many years ago and re-rendered. It is noticible against properties that were bought under the 'right to buy' and were not clad in the terrace.

The plan is the energy companies will be expected to subsidise the cost of this new external insulation, but I guess that will mean we'll all end up paying even more for our energy bills.

I have always felt that the cavity is there for good reason and to bridge the gap could potentially lead to moisture penetration from the outer skin or interstitial condensation due to reduced ventilation and/or subsequent change of temperature making dew point more probable.

A year or so ago we were getting calls about grants to have cheap cavity wall insulation. Initially I was very keen, but after a couple of hours research online I decided not to take the risk. There are quite a few examples of people who have experienced serious damp problems in 1930's houses soon afterwards. The insulation companies include so called guarantees against problems, but in practice they will just deny it is related to the insulation, and that the problem is to do with the house/build etc. No body was getting any satisfaction by complaining. (sorry I don't have any of the links now, but I'm sure yu will find the various forums etc if you look. Also beware of some "studies" into the value of cavity wall insulation I found initially which on closer inspection were far from independent!!)

It is a one way road to get the cavities filled, if you then have problems you are stuck with it. I agree that the cavities are there for a reason.

A year or so ago we were getting calls about grants to have cheap cavity wall insulation. Initially I was very keen, but after a couple of hours research online I decided not to take the risk.

Thanks Jacqui, I am coming round to that opinion. Seems too risky. I wonder if there is a solution for pasting insulated wallpaper to the inside of the house to retain some of the heat? I have searched the web and found a few articles about this which make it look an attractive option.

David

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Hi, had to reply to your post. We had the cavity of our 1950s house filled 12 years ago. We informed company at the time of survey we had problems with damp but were told it would just be condensation and this would help. We have been having damp problems ever since (not realising it would be the insulation). It has got worse in the last few years & we assumed this was due to problems with blown roughcast. A builder came & knocked some holes through to cavity & we discovered our insulation was soaking wet. Knauf insulation (contacted through CIGA via our 25 year guarantee) came out & told us that the insulation had reached saturation point (will never dry out) & was now acting as a bridge allowing the damp to cross the cavity turning our house into a giant sponge. They recommend extraction but have not agreed who is paying yet - have been waiting 8 weeks so far. This problem also happens after stormy weather when roof tiles have lifted allowing water in. My advice is be very careful there will be millions of houses where it has been successful but as your house gets older problems do happen. We never noticed any difference heat wise even when newly done. Of course this is probably because wet insulation is worse than no insulation. If you do decide to go ahead keep that guarantee in a very safe place!

Thats right if you do decide to go ahead make sure the company is registered with CIGA (Cavity Insulation Guarantee Agency) check out their website. Our installers a local company weren't interested. The company named on our guarantee had been taken over so you can see the importance of that guarantee number.

hi all i had a problem with mine after cavity walls and loft where done !!!

damp in upstairs rooms and soaking wet loft ! the company went bust and so did the guarantee so I [got a company to give me a free survey] and came back with a £162 solution !!gave them the go ahead , they fitted soffit vents and removed excess loft insulation, clean and tidy and a top job , ( which i probably could av done myself ) but for that sort of money , and was told if the problem perststs they would be happy to come back ! but assured me there would be no need !!!hey presto after redecorating the upstairs i have no damp and the loft that used to drip on me when i opened the hatch is now bone dry !just my 2 penneth but think they only cover west yorkshire may be feuther afield ? worth a try ....

Welcome to the forum. I have removed the company name because we don't allow recommendations on this forum. However, if people are interested they can send you a personal message via the forum in order to find out more.

David

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Thats right if you do decide to go ahead make sure the company is registered with CIGA (Cavity Insulation Guarantee Agency) check out their website. Our installers a local company weren't interested. The company named on our guarantee had been taken over so you can see the importance of that guarantee number.

Hi Bash 1,

Welcome to the forum. I removed the company names from your post so that it complies with forum rules.

David

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